The present invention relates to a method for handling an equipment inside a building by a crane installed outside.
Of late years, a large crane is more frequently used in a construction project and maintenance project of, for example, power station or chemical plant as a means for shortening the project schedule and making up for a lack of skilled labors and field labors. Particularly in a maintenance project, it is frequently needed to replace a component part of a product installed there.
In carrying out a replacement work, advanced operation technique to the order of millimeter is required of a large crane to avoid possible trouble such as interference with existing facilities. Such replacement work is disclosed in Japanese Laid-Open Patent Publication No. Hei 8-435777 (1996).
Generally, in removing a product out of a place, there occurs a phenomenon that, as the load of the product transfers from the installation surface of the product to the large crane, the boom of the large crane moves downward and the boom top shifts from the vertical line above the product. This means that a tension is applied from the wire to the product installed on the ground in the forward direction of the boom.
As the product is set free horizontally at the moment when being lifted off from the installation surface (as soon as the product is fully lifted up), it is swung forward by the afore-mentioned tension.
In carrying a product into a place and installing it, on the other hand, as the load of the product is transferred from the large crane to the contact surface (installation position), the boom of the large crane moves backward from the vertical line above the product and accordingly a horizontal load is applied from the wire to the product in the backward direction of the boom.
Conventionally, installation using a large crane was mostly applied to a new construction project. Because a product which required lifting operation in the course of the construction was lifted from an outdoor temporary storage yard, cares were taken so that interference with adjacent objects would be avoided even if the product swung upon the lift-off.
Beside, when carrying a product into a place, it was sufficient to rely only upon the crane operator's skill to achieve required accuracy of the carriage because the product was to be placed down on a foundation structure which was constructed in consideration of some impact.
In a maintenance project, on the other hand, if no measures are taken when removing a product out of a limited place in a building where existing facilities stand in the neighborhood of the product, it is possible that the product swings as soon as it is lifted up and may collide against the existing facilities.
Besides, when a replacement product is carried into a place and the products is adjusted to its installation position or matched to the existing mating piping, controlling the moving range of the replacement product is necessary for fine adjustment and how the afore-mentioned horizontal load from the wire can be eliminated is an important point.
As a means to solve these problems, one of the methods could be to shift the boom in the opposite direction prior to lifting up a product. According to Japanese Laid-Open Patent Publication No. Sho 64-38397 (1989), by inputting data acquired though a load test in an arithmetic unit prior to actual lifting operation, it is said to be possible to quantitatively predict at time of actual lift-off how much the boom needs to be shifted beforehand in the opposite direction for a given load. A similar method is also known according to Japanese Laid-Open Patent Publication No. Hei 1-167199 (1989).
According to Japanese Laid-Open Patent Publication No. Hei 9-79826 (1997), it is said to be possible to detect a change in the crane working radius caused by bowed deformation of the crane jib due to load, using a tachymeter employed for land survey and multiple reflecting mirrors mounted on the jib.
According to Japanese Laid-Open Patent Publication No. Hei 1-256497 (1989), by detecting a change in the boom length and derricking angle caused by deflection of the boom during actual lifting operation and correcting the derricking motion of the boom automatically, it is said to be possible to prevent swinging of a product upon lift-off. Similar methods are also known according to Japanese Laid-Open Patent Publication No. Hei 1-256496 (1989), and Laid-Open Utility Model Publication Nos. Hei 5-46882 (1993) and Hei 63-4989 (1988).